Button bleeder valve



Dec. 12, 1967 K, BRANDENBERG ETAL 3,357,675

BUTTON BLEEDER VALVE Filed NOV. 23, 1964 mm N INVENTOIQS KARL A. BRANDENBERG BY LOFPEN R. BAQT WM @fltm s.

United States Patent 3,357,675 BUTTON BLEEDER VALVE Karl A. Brandenberg, Alameda, Calif., and Loren R. Bart,

Bryan, Ohio, assignors to Moderuair Corporation, Augola, Inch, a corporation of Ohio Filed Nov. 23, 1964, Ser. No. 413,564 11 Claims. (Cl. 251-23) This invention relates generally to button bleeder valves of the type which may be employed to recycle a pneumatic control valve or the like in response to depression of a button, and is particularly directed to an improved button .bleeder valve Whose closure is internally pneumatically controlled. This application is a continuation-in-part of our application Ser. No. 191,902, filed May 2, 1962, now Patent No. 3,197,172.

Button bleeder valves are frequently employed in the control of pneumatic-ally actuated systems to facilitate recycling of a pneumatically operated control valve or the like in response to depression of the bleeder valve button. More particularly, a pair of button bleeder valves are usually respectively connected to a pair of pilot chambers of the control valve which are normally pressurized from an air supply connected thereto. Upon depression of the button of one bleeder valve the pressure in the corresponding pilot chamber is exhausted through the bleeder valve such that the pressure in the other pilot chamber actuates the control valve in one direction. In a like manner depression of the other bleeder valve button effects actuation of the control valve in the opposite direction. Where convention-a1 button bleeders are utilized for the foregoing purpose, it is necessary that the button of one be released prior to depression of the other. This precludes a number of possible control schemes which involve actuation of the control valve by depression of one button bleeder while the other button bleeder is held depressed.

Accordingly, it is an object of the present invention to provide a button bleeder valve of improved design which, when used in pairs to facilitate recycling of a pneumatically operated control valve or the like, permits actuation of the control valve with one button bleeder valve regardless of whether the other button bleeder valve is depressed or not.

Another object of the invention is the provision of a button bleeder valve of the class described whose internal control is based on pneumatic functions.

It is still another object of the invention to provide a button bleeder valve whose reclosing occurs when pressure in a bleed-off line connected thereto has dropped to a predetermined minimum without regard to the position of the button.

Yet another object of the invention is to provide a button bleeder valve of the type described which may be employed in various novel pneumatic control systems entailing recycling of pneumatically actuated means in response to depression of one button bleeder while another button bleeder valve associated with the means is held depressed.

A further object of the invention is the provision of an improved button bleeder valve of the class described which is simple and economical in construction.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawings accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawings and description may be adopted within the scope of the invention as set forth in the claims.

FIGURE 1 is a diametric sectional view of a button 3,357,675 Patented Dec. 12, 1967 bleeder valve according to the present invention, the valve being depicted in unactuated condition.

FIGURE 2 is a view similar to FIGURE 1, but with the button depressed and the valve undergoing a bleed-off phase.

FIGURE 3 is a view similar to FIGURES 1 and 2 illustrating the condition of the valve after the bleed-off has ended while the button is held depressed; and

FIGURE 4 is a schematic diagram of one pneumatic control system which is facilitated by employment therein of button bleeder valves in accordance with the present invention.

Considering now the invention in some detail and referring to the illustrated form thereof in the drawings, there will be seen to be provided a button bleeder valve which is arranged to be internally pneumatically controlled. In broad terms the valve comprises body means in which a depressible actuating button is slideably disposed and spring loaded to a normally extended position. A plunger member is also mounted within the body means in slideable relation to a recess within the button. The plunger is spring loaded to a normal position wherein a valve member carried by and movable with the plunger blocks communication between an inlet chamber and exhaust chamber which is ported to atmosphere. A valve seat is provided for the valve member. In addition the plunger and button define a sensing chamber therebetween which communicates with the inlet chamber through a passage formed in the plunger. Thus when the inlet chamber is connected to a compressed air source such as a pilot chamber of a pneumatically actuated valve, air from the source flows through the plunger passage into the sensing chamber to pressurize same. When the button is depressed, the force exerted thereon is transmitted through the air pressure in the sensing chamber to the plunger such that same moves with the button to a position opening communication between the inlet and exhaust chambers. Hence the pressure of the supply is bled from the inlet chamber to atmosphere through the exhaust chamber. Also the air in the sensing chamber is bled to atmosphere through the plunger passage and the inlet and exhaust chambers. As the pressure drops in the sensing chamber a reduced force is reached which is less than the loading spring force on the plunger. As a result the plunger moves within the depressed button to its normal position blocking communication between the inlet and exhaust chambers. Also the button and plunger are arranged to block communication between the plunger passage and sensing chamber and to port the latter to the exhaust chamber when such plunger movement occurs with the button in depressed position. Thus the bleed-oft" operation is terminated even though the button is depressed. When the button is released, the force of its loading spring returns the button to its normal extended position at the same time opening communication between the plunger passage and sensing chamber and blocking communication between the latter and the exhaust chamber.

Referring to FIGURES 1, 2, and 3 for a detailed description of our invention, the button bleeder valve is shown as comprising an elongated cylindrical body 61 having a radial exhaust port 62 at a position intermediate its length. The body includes an internal constricted portion 63 between the ports 62 and the lower end of the body as viewed in the drawing. The constricted portion partitions the body 61 into an inlet chamber and an exhaust chamber which are respectively designated at 64 and 66. Communication between the chambers 64 and 66 is provided through a central opening 67 in the constricted portion 63. The periphery of the opening 67 is bevelled on the inlet chamber side of the construction to define a valve seat 68. The end of the body defining the 3 inlet chamber (lower end of the body in the drawing) is provided with an internally threaded aperture (not shown) to facilitate connection with a pressure line in communication with the inlet chamber 64.

Slidably fitted within the opposite end of the body from the inlet chamber 64 is a depressable button designated by the numeral 71. A button recess is indicated at 72 and includes a cylindrical portion 73 extending into the internal end of the button, including cylindrical wall 77 provided at the upper end of the button which forms a chamber 75. A ball 76 which may be made of rubber or the like is urged toward a seat 78 by a spring 74. The seat 78 is held in position by a retaining ring 79 in button 71.

A plunger is designated by the numeral 80 and is preferably of elongated cylindrical form including an outwardly extending flange 81 at its upper end. The plunger 80 is coaxially disposed within the body 61 and the button recess 72. The flange 81 is of less width than a sensing chamber 92 which is formed by the cylindrical wall 73 in the button 71. The plunger is guided by having a slip fit with constricted portion 63 of the body 61.

The section of the plunger on the opposite side of flange 81 is of sutficient length to extend coaxially through the exhaust chamber 66 and into the inlet chamber 64. The lower end of the lower section of plunger 80 carries a concentric seal or valve member 84 which is engageable with seat 68 and when in engaged position blocks communication between the inlet and exhaust chambers 64 and 66. A plunger passage 82 comprises a bore in the plunger 80 extending coaxially through the plunger between its opposite ends. Preferably, the bore is constricted to define an orifice 83 adjacent its terminal opening into sensing chamber 92.

Plunger 80 is provided with passages 90 at its lower end so that communication between the inlet and exhaust chambers 64 and 66 may be effected when the valve member 84 is unseated, as shown in FIGURE 2. Plunger 80 is also provided with a protuberance 91 above flange 81 which has a flat seating portion engageable with the ball 76 when the plunger 80 is in the position shown in FIGURE 3 to lift ball 76 from its seat 78 against the bias of spring 74.

A sealing member 85 is retained at the lower end of button 71 by a washer 87 retained in position within the button 7 1 by a retaining ring 8-6. The flange 81 of plunger 80 seats on the sealing member 85 when the plunger is in the positions shown in FIGURES 1 and 2 and is unseated when in the position shown in FIGURE 3.

As regards spring loading of the button 71 and plunger 80, coil springs 38 and 89 are preferably coaxially mounted between the constricted portion 63 of body 61 and be tween the retaining ring 86 of button 81 and a flange 93 on plunger 8%), respectively. Spring 89 thus acts to urge the plunger sealing member 84 into engagement with the seat 68 to shut off communication between the inlet chamber 64 and exhaust chamber 66 and also axial openings 62. Spring 88 acts to force sealing member 85 into engagement with the lower portion of flange 81 of plunger Thus with the button bleeder valve of FIGURE 1 in its normal unactuated condition, the button and plunger are positioned relative to each other as illustrated in that figure. With a pressure line communicably connected to inlet chamber 64, air flows through the bore 82 into sensing chamber 92 as indicated by the arrows in FIGURE 1. The sensing chamber is thus pressurized.

When the button 71 is depressed, as illustrated in FIG- URE 2 to initiate a bleed off phase, plunger 80 moves with the button 71 by virtue of the pressure in sensing chamber 92. As a result, sealing member 84 is disengaged from seat 68 and thus air flows from the inlet chamber 64 through passage 90 and into the outlet chamber 66 and out through exhaust ports 62 to atmosphere. Air, likewise, flows from the sensing chamber 92 through con- 4 striction 83 and bore 82 to the inlet chamber 64 and through passages 90 to outlet chamber 66 and through exhaust ports 62 to atmosphere. The overall flow of air is as depicted by the arrows in FIGURE 2.

The pressure then drops in the sensing chamber 92 and spring 89 is able to move the plunger in a direction upwardly in the button recess 72, as shown in FIGURE 3. Sealing member 84 now engages seat 68 to block communication between the inlet and exhaust chamber 64 and 66, thus terminating the bleed-oil phase. Protuberance 91 now engages with the ball 76 to seal oil the air supply passing through bore 82 and constriction 83 of plunger 80, thus blocking communication between the sensing chamber 92 and inlet chamber 64. Also, the sensing chamber 92 is in communication with the outlet chamber 66 and exhaust ports 62 to atmosphere at this position. This provides for more positive operation of the plunger 80 to the position shown in'FIGURE 3 with less spring force. Air pressure building up in the new closed inlet chamber 64 is prevented from entering the sensing chamber 92 until the depressing force on the button is removed. When the depressing force on the button is removed, the parts return to the unactuated position shown in FIGURE 1.

By virtue of the automatic closure of the button bleeder valve of the present invention being effected in response to pneumatic pressure change without regard to the position of the button, the valve facilitates the use of various pneumatic control schemes heretofore impossible with conventional button bleeder valves. More particularly, multiposition pneumatically actuated control valves may for example be controlled by button bleeders in accordance with the present invention with one bleeder being operative to effect a shift of the control valve position even though the buttons of other bleeder valves are retained in depressed position. One example of a system which utilizes this characteristic to good advantage is depicted in FIG- URE 4, our button bleeder valve being shown at 61. As shown therein, a conventional 4-way pneumatically actuated control valve 46 is connected in controlling relation to a double acting pneumatic cylinder 47. A pair of button bleeders 48, 49 are respectively connected to the pilot chambers of the control valve. When button bleeder 48 is depressed, the corresponding pilot chamber of the control valve is bled to atmosphere and the control valve established flow conditions extend the piston rod 51 of cylinder 47. When button bleeder 49 is depressed the other pilot chamber of the control valve is bled to atmosphere and the flow conditions to the cylinder are reversed to retract piston 51.

A second double acting pneumatic cylinder 52 is similarly controlled by a 4-way control valve 53. In this in stance, however, a button bleeder valve (61) in accordance with the present invention is connected to one pilot chamber of valve 53, and this bleeder is disposed to be depressed by piston rod 51 in its extended position. The other pilot chamber of valve 53 is connected to button bleeder 49. When piston rod 51 is extended and button bleeder valve 6 1 is thereby depressed, the corresponding pilot chamber of valve 53 is bled to atmosphere to effect flow conditions to the cylinder 52 productive of extension of its piston rod 56. Even though button bleeder valve 61 is held depressed by piston rod 51, bleeder 49 may be depressed to return both piston rods 51 and 56 to their retracted positions.

While one embodiment of the invention has been shown and described herein, it will be understood that it is illustrative only and not to be taken as a definition of the scope of the invention, reference being had for this purpose to the appended claims.

What is claimed is:

1. A button bleeder valve comprising a hollow body, a button slideably disposed within a first end of said body, said button having a recess is in its inner end, means normally urging said button to an extended position from said first end, means defining inlet and exhaust chambers in said body communicating through a passage including a valve seat, said inlet chamber being adapted for connection to a pressurized air source, said exhaust chamber being ported to atmosphere, a plunger slideably disposed within said hollow body, and projecting into said button and defining a sensing chamber therewith, a valve merriber carried by said plunger and movable therewith, said plunger in the direction of the outer end of said button to said first position, said sensing chamber being placed in communication with said exhaust chamber through said passage in the plunger when the button is initially depressed and the plunger is thereby moved to said second position, said valve member comprising means blocking said communication through said first mentioned passage when said button is held in its depressed position and said plunger is returned to its said first position, a closure element carried by said button, engageable with the adjacent end of said plunger to close the sensing chamber end of said passage of said plunger and resiliently urged with respect to said button in a direction toward said plunger, and means for returning said plunger to its first position when said sensing chamber and exhaust chamber are in communication.

2. A button bleeder valve comprising a hollow body, a button slideably disposed within a first end of said body, said button having a recess in its inner end, means normally urging said button to an extended position from said first end, means defining inlet and exhaust chambers in said body communicating through a passage including a valve seat, said inlet chamber being adapted for connection to a pressurized air source, said exhaust chamber being ported to atmosphere, a plunger slideably disposed within said hollow body, and projecting into said button and defining a sensing chamber therewith, a valve member carried by said plunger and movable therewith, said plunger being movable between a first position wherein said valve member engages said valve seat to block communication between said inlet and said exhaust chambers and being movable to a second position disengaging said valve member from said valve seat to establish communication between the inlet and exhaust chambers, said plunger having a passage extending between said inlet and said sensing chambers, means normally urging said plunger in the direction of the outer end of said button to said first position, said sensing chamber being placed in communication with said exhaust chamber through said passage in the plunger when the button is initially depressed and the plunger is thereby moved to said second position, said valve member comprising means blocking said communication through said first mentioned passage when said button is held in its depressed position and said plunger is returned to its said first position, a closure element carried by said button, engageable with the adjacent end of said plunger to close the sensing chamber end of said second mentioned passage to thereby block flow from said inlet chamber to said sensing chamber, and means for thereafter returning the button to its initial position and thereby spacing said closure element from said adjacent end of said plunger.

3. A button bleeder valve comprising a hollow body, a button slidably disposed within a first end of said body, said button having a recess in its inner end, means normally urging said button to an extended position from said first end, means defining inlet and exhaust chambers in said body communicating through a passage including a valet seat, said inlet chamber being adapted for connection to a pressurized air source, said exhaust chamber being ported to atmosphere, a plunger slideably disposed within said hollow body, and projecting into said button and defining a sensing chamber therewith, a valve member carried by said plunger and movable therewith, said plunger being movable between a first position wherein said valve member engages said valve seat to block communication between said inlet and said exhaust chambers and being movable to a second position disengaging said valve member from said valve seat to establish communication between the inlet and exhaust chambers, said plunger having a passage extending between said inlet and said sensing chambers, means normally urging said plunger in the direction of the outer end of said button to said first position, said sensing chamber being placed in communication with said exhaust chamber through said passage in the plun er when the button is initially depressed and the plunger is thereby moved to said second position by movement of said button, said valve member comprising means blocking said communication through said first mentioned passage when said button is held in its depressed position and said plunger is returned to its said first position, a blocking element carried by said button, said passage of said plunger being blocked by said blocking element from communication with said sensing chamber while said button is held in the depressed position when said first passage is blocked.

4. A button bleeder valve comprising a hollow body, a button slideably disposed within a first end of said body, said button having a recess in its inner end, means normally urging said button to an extended position from said first end, means defining an inlet chamber in a second end of said body adapted for connection to a pressurized air source, means defining an exhaust chamber in said body intermediate said first and second ends and in coaxial communication with said inlet chamber through a passage including a valve seat, said exhaust chamber ported to atmosphere, a plunger slidably disposed within said holhlow body, and projecting into said recess of said button and defining a sensing chamber therewith, said plunger projecting from said recess coaxially through said exhaust chamber and passage into said inlet chamber, said plunger having a passage extending from said inlet chamber to said sensing chamber, seal means carried by said plunger for engaging said seat and blocking communication between said inlet and exhaust chambers in a first position of movement of said plunger towards said button and dis engaged from said seat and establishing communication between said inlet and exhaust chambers in a second position of movement of said plunger towards said inlet chamber, means normally urging said plunger to said first position, said valve member comprising means blocking communication through said passage of said plunger and establishing communication between said sensing and exhaust chambers when said button is depressed and said plunger is returned to said first position, and means carried by said button and resiliently engageable with said passage of said plunger to seal the same against flow from said sensing chamber also when said button is depressed and said plunger is returned to said first position.

5. A button bleeder valve comprising a hollow cylindrical body having an internal constricted portion intermeidate the first and second ends thereof, said body having radial ports at a position intermediate the constricted portion and first end thereof, a button slideably disposed within said first end of said body, said button having a recess in its internal end, said recess having a first portion connected by an outwardly extending transition region to a second portion of enlarged diameter in turn connected to an inwardly stepped third portion of reduced diameter, means spring loading said button to a normal position extended from said first end of said body, a plunger coaxially disposed within said body, said plunger having an outwardly flared flange movable within said second portion of said recess, said plunger having a first end projecting from said flange into said second portion of said recess, said plunger having a second end projecting from said flange through said constricted portion, said plunger having a passage extending between its first and second ends, means spring loading said plunger in the direction of the first end of said body, retention means secured adjacent the outer end of said second portion of said recess and engable with said flange, seal means carried by the second end of said plunger sealingly engageable with said constricted portion on the proximal side thereof relative to said second end of said body, said flange being sealingly engageable with said retention means and third seal means carried by said button and sealingly engageable with said passage of said plunger to close the same when said flange is disengaged from said retention means.

6. A button bleeder valve according to claim 5, further defined by said passage being a coaxial bore through said plunger having an orifice defining constriction adjacent the first end thereof which is engagable by said third seal means.

7. A button bleeder valve according to claim 6, further defined by said means spring loading said button comprising a coil spring disposed between said constricted portion of said body and said retention means, and said means spring loading said plunger comprising a second coil spring disposed between said constricted portion of said body and said flange.

8. A button bleeder valve comprising a hollow body, a button slidably disposed within a first end of said body, said button having a recess in its inner end, means normally urging said button to an extended position from said first end, means defining inlet and exhaust chambers in said body communicating through a passage including a valve seat, said inlet chamber being adapted for connection to a pressurized air suorce, said exhaust chamber being ported at atmosphere, a plunger slidebly disposed within said hollow body, and projecting into said button and defining a sensing chamber therewith, a valve member carried by said plunger and movable therewith, said plunger being movable between a first position wherein said valve member engages said valve seat to block communication between said inlet and said exhaust chambers and being movable to a second position disengaging said valve members from said valve seat to establish communication between the inlet and exhaust chambers, said plunger having a passage extending between said inlet and said sensing chambers, means normally urging said plunger in the direction of the outer end of said button to said first position, said sensing chamber being placed in communication with said exhaust chamber through said passage in the plunger when the button is initially depressed and the plunger is thereby moved to said second position said valve member comprising means blocking said communication through said first mentioned passage when said button is held in its depressed position and said plunger is returned to its said first position, said sensing chamber being still in communication with said exhaust chamber when the button is held in its depressed position and the plunger is returned to its first position, and a closure element for said passage of said plunger carried by said button and closing said passage upon return of said plunger to said first position and while said button is held depressed.

9. A button bleeder valve comprising a hollow body, a button slideably disposed within a first end of said body, said button having a recess in its inner end, means normally urging said button to an extended position from said first end, means defining inlet and exhaust chambers in said body communicating through a passage ineluding a valve seat, said inlet chamber being adapted for connection to a pressurized air source, said exhaust chamber being ported to atmosphere, a plunger slideably disposed within said hollow body, and projecting into said button and defining a sensing chamber therewith, a valve member carried by said plunger and movable therewith, said plunger being movable between a first position wherein said valve member engages said valve seat to block communication between said inlet and said exhaust chambers and being movable to a second position disengaging said valve member from said valve seat to establish communication between the inlet and exhaust chambers, said plunger having a passage extending between said inlet and said sensing chambers, means normally urging said plunger in the direction of the outer end of said button to said first position, said sensing chamber being placed in communication with said exhaust chamher through said passage in the plunger and when the button is initially depressed the plunger is moved to said second position by movement of said button, valve member comprising means blocking said communication through said first mentioned passage when said button is held in its depressed position and said plunger is returned to its said first position, said means for blocking the passage in the plunger comprising a seat on the plunger and a biased ball retained within the body.

19. A button bleeder valve comprising a hollow body, a button slideably disposed within a first end of said body, said button having a recess in its inner end terminating in a button valve seat, means normally urging said button to an extended position from said first end, means defining inlet and exhaust chambers in said body communicating through a passage including a valve seat, said inlet chamber being adapted for connection to a pressurized air source, said exhaust chamber being ported to atmosphere, a plunger slidably disposed within said hollow body, and projecting into said button and defining a sensing chamber therewith, a valve member carried by said plunger and movable therewith, said plunger being movable between a first position wherein said valve member engages said valve seat to block communication between said inlet and said exhaust chambers and being movable to a second position disengaging said valve member from said valve seat to establish communication between the inlet and exhaust chambers, said plunger having a passage extending between said inlet and said sensing chambers, means normally urging said plunger in the direction of the outer end of said button to said first position, said sensing chamber being placed in communication with said exhaust chamber through said passage in the plunger when the button is initially depressed and the plunger is thereby moved to said second position, said valve member comprising means blocking said communication through said first mentioned passage when said button is held in its depressed position and said plunger is returned to its said first position, said plunger having a flange thereon adjacent the top to engage said button valve seat before said button is depressed and when it is initially depressed, said flange being smaller than the recess in the button in which it moves and passage blocking means carried by said button and engageable with the sensing chamber end of said passage of said plunger at the time said button is held in its depressed position and said plunger is returned to its said first position.

11. A button bleeder valve comprising a hollow body, a button slideably disposed within a first end of said body, said button having a recess in its inner end, means normally urging said button to an extended position from said first end, means defining inlet and exhaust chambers in said body communicating through a passage including a valve seat, said inlet chamber being adapted for connection to a pressurized air source, said exhaust chamber being ported to atmosphere, a plunger slideably disposed within said hollow body, and projecting into said button and defining a sensing chamber therewith, a valve member carried by said plunger and movable therewith, said plunger being movable between a first position wherein said valve member engages said valve seat to block communication between said inlet and said exhaust chambers and being movable to a second position disengaging said valve member from said valve seat to establish communication between the inlet and exhaust chambers, said plunger having a passage extending between said inlet and said sensing chambers, means normally urging said plunger in the direction of the outer end of said button to said first position, said sensing chamber being placed in communication with said exhaust chamber through said passage in the plunger when the button is initially depressed and the plunger is thereby moved to said second position, said valve member comprising means blocking said communication through said first mentioned passage when said button is held in its depressed position and said plunger is returned to its said first position, said button having a stop seat, a closure element carried by said but- References Cited UNITED STATES PATENTS 3,197,172 7/1965 Brandenberg et a1. 251-23 FOREIGN PATENTS 4,225 1-833 Great Britain.

M. CARY NELSON, Primary Examiner.

ton and resiliently engageable with the side of said stop 15 ROSENTHAL, Assistant Examiner- 

1. A BUTTON BLEEDER VALVE COMPRISING A HOLLOW BODY, A BUTTON SLIDEABLY DISPOSED WITHIN A FIRST END OF SAID BODY, SAID BUTTON HAVING A RECESS IS IN ITS INNER END, MEANS NORMALLY URGING SAID BUTTON TO AN EXTENDED POSITION FROM SAID FIRST END, MEANS DEFINING INLET AND EXHAUST CHAMBERS IN SAID BODY COMMUNICATING THROUGH A PASSAGE INCLUDING A VALVE SEAT, SAID INLET CHAMBER BEING ADAPTED FOR CONNECTION TO A PRESSURIZED AIR SOURCE, SAID EXHAUST CHAMBER BEING PORTED TO ATMOSPHERE, A PLUNGER SLIDEABLY DISPOSED WITHIN SAID HOLLOW BODY, AND PROJECTING INTO SAID BUTTON AND DEFINING A SENSING CHAMBER THEREWITH, A VALVE MEMBER CARRIED BY SAID PLUNGER AND MOVABLE THEREWITH, SAID PLUNGER BEING MOVABLE BETWEEN A FIRST POSITION WHEREIN SAID VALVE MEMBER ENGAGES SAID VALVE SEAT TO BLOCK COMMUNICATION BETWEEN SAID INLET AND SAID EXHAUST CHAMBERS AND BEING MOVABLE TO A SECOND POSITION DISENGAGING SAID VALVE MEMBER FROM SAID VALVE SEAT TO ESTABLISH COMMUNICATION BETWEEN THE INLET AND EXHAUST CHAMBERS, SAID PLUNGER HAVING A PASSAGE EXTENDING BETWEEN SAID INLET AND SAID SENSING CHAMBERS, MEANS NORMALLY URGING SAID PLUNGER IN THE DIRECTION OF THE OUTER END OF SAID BUTTON TO SAID FIRST POSITION, SAID SENSING CHAMBER BEING PLACED 